1. Field of the Invention
The present invention relates to an ink for a ball point pen, specifically to an ink for a ball point pen which is prevented from leaking out of the pen tip and is not damaged smooth writing feeling and which does not cause clogging at the pen tip.
2. Description of the Related Art
Ball point pens filled with conventional inks having a viscosity of 5000 to 20000 mPa.multidot.s at 25.degree. C. sometimes leak the inks from the pen tips when the ball point pens have been irradiated directly with sunlight to have the temperatures of the pen bodies elevated, or when the ball point pens have been left turning downward for long time. Ball point pens filled with inks having a low viscosity of 1000 to 5000 mPa.multidot.s at 25.degree. C. show such tendency more markedly. Increasing the drying property of inks in order to stop leaking of the inks brings about the problems of deterioration in the writing feeling, starving at the beginning of writing and reduction in the shelf life.
Furthermore, inks leaking out of the pen tips of ball point pens stain hands and cloths or make it impossible to use the ball point pens in a certain case. Accordingly, it is the current situation to prevent inks from leaking by reducing clearance of tips, and thus the writing feeling tends to be deteriorated.